Kolbe U.S. Pat. No. 2,953,126 discloses an engine coolant distribution arrangement in an internal combustion engine having a flow path extending, from a water pump at the front of the engine, longitudinally through the cylinder block from one end to the other and from which portions of the coolant flow are bled off to create parallel flow paths through the cylinder head. In order to obtain more uniform engine cooling, the passages leading to the cylinder head coolant passages from the engine block coolant block passages are graduated so that the smallest passages are adjacent the block coolant entry passage and the largest passage is at the opposite end of the cylinder block coolant passage.
In a comparable manner, Beardsley U.S. Pat. No. 2,713,332, discloses an internal combustion engine cooling system wherein the coolant inlet manifold extends longitudinally, from a pump in front of the engine, along a cylinder bank and coolant is delivered from it into a distributing header where the flow is divided; a portion of the coolant travelling through the cylinder head to an outlet in a manner passing over the valve guides, while another portion of the coolant passes through openings into a cylinder block jacket where it circulates around the cylinders. In order to balance the coolant flow, the effective cross sectional area of the inlet manifold progressively decreases from the end thereof connected to the pump to its opposite end remote from the pump and the openings through which coolant travels from the inlet manifold into the cylinder head are constructed such that the openings nearest the pump have a slightly smaller cross-sectional area than those disposed at the opposite end of the inlet manifold.
While coolant flow arrangements of the above-noted type do obtain some improvement in terms of balancing the cooling effect, a mere progressive change in the size of the flow passages between the cylinder head and the cylinder block does not take into account various other factors which affect the ability for the coolant to achieve an equalized heat absorbing effect. Fahlman U.S. Pat. No. 2,188,876, discloses a cylinder head for an engine wherein coolant enters the cylinder block at the front end of the engine and exits the engine at a longitudinally central point at one side of the cylinder head, and that is designed for obtaining a substantially uniform temperature around the combustion chambers and an equalized cooling effect. To do so, Fahlman not only takes into account the distance of the passages between the head and block from the coolant inlet, but also takes into account the fact that parts of the engine will have different cooling requirements than other parts.
Accordingly, to obtain a uniform temperature around all of the combustion chambers, the size of the inlets from the coolant jacket of the engine block into the cylinder head and the cross-sectional area of the flow passages along the cylinder head are varied to obtain a rate and quantity of flow across the cylinder head which will produce a uniform cooling effect (i.e., will distribute the cooling capacity of the coolant so that the hottest parts receive the greatest cooling effect). In particular, the head is treated in stages corresponding to respective sides of each of the combustion chambers (5 stages in a 4 cylinder engine) with the relative flow being proportioned from section to section and within each section.
For the stage closest the engine block coolant jacket inlet, the area of the inlet passages account for 24% of the total area, while those of the stage furthest therefrom account for 37% of the total area. Furthermore, the passages in the central stage (stage nearest the outlet from the cylinder head) account for 17% of the total area while the passages of the adjacent stage on the side toward the jacket inlet account for 14% of the total inlet area and the stage between the central stage and the stage furthest from the jacket inlet has inlet passages accounting for 59% of the total inlet area. Additionally, the inlet passages within each stage are proportioned in accordance with the noted criterion and thus do not have areas whose size correlate directly with their positional pattern. For example, the central stage has three inlet passages of progressively increasing size in a first transverse direction while the stages adjacent thereto each have two different size pairs of equal area inlet passages with the larger one pair of passages of one of these adjacent stages being located on the opposite side of the engine relative to the larger pair of inlet passages of the other adjacent stage.
However, in addition to the complexities of implementing Fahlman's method of cooling an internal combustion engine, the disclosure of this patent fails to take into consideration the fact that a fuel supply system, such as a fuel injector, and a valve arrangement normally are situated in the cylinder head and place practical limitations on the manner in which coolant may be circulated (the engine disclosed in U.S. Pat. No. 2,188,876 having no fuel supply means or valves associated with its engine cylinders).
U.S. Pat. No. 4,284,037, owned by the assignee of the present application, discloses an internal combustion engine coolant system having coolant feed and collection manifolds provided on one side of the cylinder block adjacent each other, and a coolant pump mounted adjacent to and connected with the manifolds on the block. For each cylinders, separate flow passages are formed on the block which conduct the coolant from the feed manifold around the cylinder, up and into the head, across the head and adjacent the injector and the valves, and then down from the head into the collection manifold on the block.
The respective flow paths of coolant through the head are substantially separated and the sizes of the flow passages associated with the various paths are designed to obtain a uniform heat transfer pattern among the various cylinders by controlling the quantity of flow in each path and by providing a valve orientation wherein, for each cylinder, two valves are on the longitudinal axis of the head and another two are on a line that is perpendicular to this axis. Along with partition walls which prevent the coolant from flowing straight across the head, this arrangement forces the coolant to flow at 45 degree angles between pairs of valves to and from the injector, the coolant flowing above and below the exhaust passages after having passed the injector. Additionally, the exhaust ports are relatively close to the exhaust manifold side of the head and the exhaust passages are relatively short, whereby the heated exhaust is removed from the head as quickly as possible.
However, problems exist in adapting such an engine configuration to engines wherein all of the cylinder valves are arranged in a longitudinally extending line, a single pair of closely spaced valves being provided at each cylinder and the injector being situated at a lateral side of the valves opposite the coolant feed and collection manifolds. For example, the cross paths can no longer be maintained and the laterally positioned injector interferes with cooling of the valves by the flow coming across the head after having come up from the cylinder block, since the injector partially shields same. On the other hand, obtaining of the most compact configuration for the engine (for purposes of minimizing weight and space requirements), as well as other considerations, make it impossible to place the various parts so as to facilitate coolant distribution.